Origin of the superconductivity in the Y-Sr-Ru-O and Y-Sr-Cu-O systems

We report on the structural, magnetic, and Raman-scattering studies of double-perovskite structure Sr₂YRu_1-xCu_xO_6-δ systems made by systematic synthesis processes with various numbers of doping concentrations and sintering temperatures. We observed different behaviors resulting from the different thermal treatments. In particular, superconductivity in Cu-doped Sr₂YRuO₆ has been observed only for partially melted ceramic materials. We show that superconductivity is associated with the 1:2:3 phase (YSr₂Cu₃O_t) , similar to that of Y-Sr-Cu-O samples sintered at high temperature.